Field of the Invention
This invention relates in general to the machining of preferably optical surfaces or workpieces, especially mirrors or lenses, especially preferably by face turning. In particular, this invention relates to a linear drive and to a use of this linear drive for mechanical treatment or machining, preferably turning and face turning, of a preferably optical or metallic workpiece, especially an optical surface or lens.
Description of Related Art
This invention relates especially to machining on a lathe and to face turning. By means of a linear drive which is often also called a fast tool drive or fast tool arrangement, a tool, especially a turning tool or lathe tool, depending on the rotary position of the work which is to be machined, is moved or fed linearly. In particular, back and forth motion and also oscillating motion or reciprocating motion take place. Thus, especially non-rotationally symmetrical machining can take place and non-rotationally symmetrical surfaces or free-form surfaces can be produced, in particular to implement desired optical properties of an optical component such as a mirror or a lens.
European Patent Application EP 1 647 360 A2 and corresponding U.S. Pat. No. 7,357,054 B2 show a linear drive in the aforementioned sense with a linearly movable rotor which bears a tool for machining. The rotor is movably mounted in bearings via leaf springs. The high forces at high accelerations of the rotor and vibrations and inaccuracies resulting therefrom during machining are problems.
German Patent Application DE 10 2005 052 314 A1, which corresponds to U.S. Pat. No. 8,056,453 B2, shows a linear drive with an air-cushioned rotor. The high forces at high accelerations of the rotor and vibrations and inaccuracies resulting therefrom during machining are problems.
International Patent Application Publication WO 97/13603 A2 and corresponding U.S. Pat. No. 6,523,443 B1 disclose a machine tool for machining of optical surfaces, on a stiff machine bed a spindle being mounted on which a blank for optical surface machining can be held. A first linear drive bears a turning tool which can be moved in the axial direction of the spindle. For dynamic mass compensation, the machine tool has a second linear drive which is located collinearly to the first linear drive and whose housing or stator is mechanically coupled to the housing or stator of the first linear drive via the machine bed and which is triggered in the opposite direction to the first linear drive. The machine tool and the linear drives which are provided are structurally very large. The linear drives are relatively inert and are not optimized in particular for rapid, highly dynamic movement.
German Patent Application DE 198 10 996 A1 and corresponding U.S. Pat. No. 6,744,155 B1 disclose a momentum-decoupled direct drive with a movable driven part and an assigned reaction part which is built especially as a primary part with electrical windings. The reaction part is movably supported on a substructure so that when the driven part moves the reaction part executes an opposite motion. Therefore, this direct drive is built only of one linear motor. In particular, the reaction part is coupled to the substructure via a spring element. Optimum compensation or momentum decoupling therefore cannot be achieved.
German Utility Model DE 200 19 035 U1, which corresponds to U.S. Patent Application Publication 2002/0057952 A1, discloses a machine tool with a linearly movable slide which bears a tool. In order to preclude mass forces of the slide which is to be accelerated vertically, there is weight compensation from two compensating masses which work in opposite directions. The compensating masses are each coupled to the slide via pinions which are connected to drives which are not shown, the pinions on the one hand meshing with racks of the slide and on the other with racks of the compensating masses. Therefore, here, there is mechanical coupling of the movable slide to the compensation masses, and a rotary drive, especially therefore not a direct drive. This structure is unsuited or too slow for the especially intended machining of optical surfaces or workpieces.